The present invention relates to a stand for instruments of metal, such as root canal files, nerve extractors, drills and the like, for use in the field of medicine, particularly odontology.
Various materials and instruments with extremely specific properties and design are used for root filling or endodontic treatment.
Examples of such instruments are root canal files and nerve extractors which are characterized, inter alia, by comparatively slim dimensions, but upon which, nevertheless, considerable demands for strength are placed. Other properties are great flexibility to enable the finely branched anatomy of the root canals to be followed. Another necessary property of the instruments is sharp edges to enable efficient mechanical clearing of the walls of the root canal.
In all endodontical treatment all operations must be performed using aseptic methods in order to prevent the spread of infection.
This means, for instance, that the instruments used must be sterilized in a reliable manner, i.e. either by means of autoclave sterilization in saturated water vapour at 120.degree.-130.degree. C. for 10-20 minutes or by means of dry sterilization at 180.degree. C. with a sterilization time of 90 minutes. It has long been recognized that treating root canal instruments with conventional sterilizing techniques causes considerable damage to the instruments, primarily due to corrosive attacks which deteriorate the sharpness of the edges and greatly increase the risks of the instruments breaking when used.
In view of the high demands placed on their cutting ability, root canal instruments are preferably made of carbon steel (compare scalpels). However, carbon steel is attacked by oxygen in the air and even more so in a moist heat such as that occurring in autoclave sterilization.
The relatively high temperature required for dry sterilization also affects the carbon steel instruments unfavourably, increasing the brittleness of the material, deteriorating the edge sharpness and causing oxidation deposits on the surface of the instruments.
However, in comparison with autoclave sterilization, sterilization with dry heat causes less destruction to these instruments. Since it is becoming more and more usual to change over to autoclave sterilization in the odontological field too, the problem of damage to the instruments is being accentuated.
In order to avoid the unfavourable effects caused by the inescapable sterilization procedures described, the root canal instruments have been surface treated, for instance by chromium-plating them at the manufacturing stage. Admittedly this provides better protection against corrosion but on the other hand the edge loses its sharpness due to the surface treatment.
Other methods of solving the problem are to provide the instruments with a thin coating of some corrosion inhibitor immediately prior to sterilization, either by spraying the instruments with an inhibitor solution or by dipping them in the solution. With autoclave sterilization it is also possible to add a water soluble corrosion inhibitor to the water in the autoclave, which is then vaporized together with the water upon heating.
However, none of the proposed solutions have given a satisfactory result when applied to root canal instruments, possibly because it is impossible to maintain a sufficient concentration of the corrosion inhibitors throughout the sterilization cycle.
The instruments must be placed in special file stands to enable them to be gripped directly with thumb and index finger without contaminating the rest of the instruments. Placing the instruments in file stands of metal also contributes to increased corrosion due to the electrolytic action which occurs upon contact between different metals.